J&J COVID-19 Vaccine: What You Need to Know

With SMH Infectious Disease specialist Manuel Gordillo, MD

After a 10-day pause, the federal Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) gave the green light for the single-dose Johnson & Johnson-Janssen COVID-19 vaccine to again be administered in the United States. 

Earlier this month, the agencies recommended the pause on distribution of the Johnson & Johnson (J&J) vaccine due to reports of adverse health issues among a small group of J&J vaccine recipients. The group, 15 women ages 18 to 59, all developed a serious blood clot and low platelet condition called thrombosis with thrombocytopenia syndrome (TTS) within weeks of being vaccinated. 

The “unpause” on April 23 followed a review of these cases and the vaccine’s potential risks by an independent panel of experts. Based on available data, the committee found that the benefits of the J&J COVID-19 vaccine outweigh its risks for those recommended to receive it. 

We know you still have questions about the J&J vaccine. Here, Sarasota Memorial Infectious Disease specialist Manuel Gordillo, MD, answers those questions and shares the latest guidance from the CDC. 

Is the J&J Vaccine Safe?

In their joint announcement lifting the pause, the agencies said that based on the experts’ in-depth analysis, they are confident the J&J vaccine is safe and effective in preventing COVID-19 among those age 18 and older.

However, women younger than 50 should be aware of the rare but increased risk of TTS, the CDC advises, and should know that there are other COVID-19 vaccine options available for which this risk has not been seen.

Of the more than 8 million doses of the J&J vaccine administered in the U.S., 15 TTS cases have been reported among recipients, as of April 23. For all women, this is a rare adverse event (and even more rare among men), occurring at a rate of 7 per 1 million vaccinations among women 18 through 49 years old and less than 1 per million vaccinations among women 50 years and older. To put it in perspective, the number of women who experience blood clots due to birth control is 500 to 1,200 in 1 million.

At this time, there is no genetic evidence that women are more or less likely to experience this rare complication.

I Got the J&J Vaccine. Should I Worry? 

J&J vaccine recipients need not worry unless they experience significant side effects (see list below) 1 to 4 weeks after vaccination. If you received the vaccine within the last 3 weeks, your risk of developing a blood clot is very low and will decrease further by Week 4. 

The signs of this blood-clotting disorder are different than the vaccine’s more common side effects (like mild headaches or flu-like symptoms), which are seen within days of vaccination. 

What Red Flag Symptoms Should I Look For?

You should contact your healthcare provider and seek urgent medical treatment if you develop any of the following red-flag symptoms within the first 4 weeks of receiving the J&J vaccine:

• Severe headache, backache or abdominal pain


• New neurologic symptoms


• Shortness of breath


• Leg swelling


• Tiny red spots on the skin (petechiae) or new / easy bruising

Although rare, the clotting syndrome can be treated, but it is important to let your healthcare provider know whether you received the Johnson & Johnson vaccine because the condition will be treated differently than a typical blood clot.

Why Was the J&J Vaccine ‘Paused’?

The FDA and CDC have many systems in place to find, report and investigate any possible vaccine-related adverse events. The adverse events among the J&J vaccine recipients that sparked the pause were all reported through the Vaccine Adverse Event Reporting System (VAERS). The agencies’ swift action in the J&J cases is evidence that this system of vaccine safety checks and balances is working.

The pause also gave experts time to carefully review all available data, conduct a risk-benefit analysis of the J&J vaccine’s use and allowed the CDC to communicate with medical providers to make sure they are able to recognize and appropriately treat this completely new condition, a very important step in mitigating the potential consequences. At SMH, we diligently informed and familiarized all of our healthcare providers on this issue.

Has this Clotting Been Seen Among Recipients of Other Vaccines?

The clots have not been associated with the Pfizer-BioNTech or Moderna vaccines, which are both mRNA vaccines requiring 2 doses. They use different technologies than the J&J vaccine, which is a one-dose adenovirus vector vaccine. 

There have been no major safety concerns or similar events reported with more than 180 million doses of Pfizer and Moderna vaccines already administered.   

Are Health Officials Concerned the Clotting Was Caused by the J&J Vaccine?

The rare clotting disorder – cerebral vein sinus thrombosis – can occur independently of a vaccine. Low platelets can also occur independently of the vaccine. It is the combination of the cerebral vein sinus thrombosis with low platelets that has caused concern that it may be related to the vaccine. Although extremely rare, it is also possible these patients would have developed these clots without having been vaccinated. 

It is important to note that this rare clotting disorder is different from more common blood clots in the lungs or leg veins, affecting 300,000 to 600,000 Americans every year. Among people with normal platelet counts, the disease affects 2 to 14 per 1 million people per year.

Is There a Link Between the Adverse Events and Birth Control?

Although all of the known cases are among vaccinated women of childbearing age, it’s not clear yet whether there’s any association with birth control. Cerebral venous sinus thrombosis is seen among women using hormonal forms of birth control that raise the risk of such clots. 

Women concerned about possible symptoms related to the vaccine and contraception should consult their doctor.

Until there is a better understanding of the frequency and impact of this finding, the American College of Obstetricians and Gynecologists (ACOG) encourages pregnant and postpartum women who wish to be vaccinated to receive the mRNA vaccines: Pfizer or Moderna. ACOG is reviewing the latest CDC and FDA recommendations and may update its guidance in the coming days. Click here for updates.

Why Should I Get the J&J Vaccine When Others are Available?

All of the current COVID-19 vaccines offer significant protection against COVID-19-related hospitalization and death. 

A single death is one too many, which underscores the value of COVID-19 vaccines. The blood clot disorder is extremely rare, affecting 7 per 1 million women age 18 to 49 and fewer than 1 per 1 million women older than 50. 

By comparison, approximately 20 women of this age range die each day from COVID-19 in the US. These deaths occur disproportionally among people of color, people with lower incomes, those who are homeless and those with comorbidities. These are precisely the vulnerable groups in which a single-dose vaccine would have the greatest impact in simplifying logistics, easing access barriers and reducing vaccine hesitancy.  

** NOTE: This content was originally posted April 27, 2021. Information related to COVID-19 and COVID-19 vaccines is continually evolving. For the most up to date info, we recommend visiting cdc.gov.